System and method for determining a security encoding to be applied to outgoing messages

ABSTRACT

A system and method for determining a security encoding to be applied to a message being sent by a user of a computing device, such as a mobile device, for example. In one broad aspect, the method comprises the steps of identifying a message to be sent to at least one recipient; determining, at the computing device, whether a general message encoding configuration setting thereon is set to a value that indicates that the security encoding to be applied to the identified message is to be established by a policy engine; where the general message encoding configuration setting on the computing device is set to a value that indicates that the security encoding to be applied to the identified message is to be established by the policy engine, determining the security encoding to be applied to the identified message by querying the policy engine for the security encoding to be applied to the identified message; applying the determined security encoding to the identified message; and transmitting the identified message to which the security encoding has been applied to the at least one recipient. In one embodiment, the policy engine is a PGP Universal Server.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/686,050, filed Jun. 1, 2005, the contents of which are hereinincorporated by reference.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF THE INVENTION

Embodiments of the invention relate generally to the processing ofmessages, such as e-mail messages, and more specifically to systems andmethods for controlling the application of security encoding techniques(e.g. encryption, signing) to messages being sent by users of computingdevices (including, for example, mobile devices).

BACKGROUND OF THE INVENTION

Electronic mail (“e-mail”) messages may be generally encoded using oneof a number of known protocols to facilitate secure messagecommunication. The Secure Multiple Internet Mail Extensions (“S/MIME”)protocol, for example, relies on public and private encryption keys toprovide confidentiality and integrity, and on a Public KeyInfrastructure (PKI) to communicate information that providesauthentication and authorization. Data encoded using a private key of aprivate key/public key pair, can only be decoded using the correspondingpublic key of the pair, and vice-versa. In S/MIME, the authenticity ofpublic keys used in the encoding of messages may be validated usingcertificates. Other known standards and protocols may be employed tofacilitate secure message communication, such as Pretty Good Privacy™(PGP) and variants of PGP such as OpenPGP, for example. It is understoodthat as compared to S/MIME-based systems, PGP-based systems also utilizepublic and private encryption keys to provide confidentiality andintegrity, although the authenticity of public keys used in the encodingof PGP messages are validated in a different manner.

When a user wishes to send a message to be encrypted (e.g. using S/MIMEor PGP), message data will be encrypted using the public key of aprivate key/public key pair associated with the intended recipient ofthe message, such that the encrypted message data can only besubsequently decrypted by the corresponding private key of the same pairsupposedly possessed only by the recipient. In some implementations, asession key is encrypted/decrypted, rather than the message itself. Whena user wishes to send a message that is to be digitally signed (e.g.using S/MIME or PGP), a digest generated from the message will beencoded using the private key of a private key/public key pairassociated with the user (i.e. the sender of the message in thisexample) to produce a digital signature, such that the signature canonly be successfully verified using the corresponding public key of thesame pair.

After a user composes a message and before it is sent, the user cantypically decide what encoding, if any, is to be applied to the message.For example, the user may choose to encrypt the message without signing,to sign the message without encrypting, to both encrypt and sign themessage, or to send the message unencrypted and unsigned. Some knownmessaging applications may be adapted to analyze certain data andsuggest a security encoding for messages to the user. For example, themessaging application may determine that the composed message is a replyto a received message that has been encoded in a certain way, andsuggest to the user that the same security encoding be applied to thecomposed message. As a further example, the messaging application may beconfigured to track the security encoding applied to previous messagessent by the user to particular recipients, and suggest to the user thatthe same security encoding should be applied to the composed message ifthe message is intended to be sent to one or more of those recipients.In any event, the user is free to select the desired security encodingfor any given message that he or she composes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the systems and methodsdescribed herein, and to show more clearly how they may be carried intoeffect, reference will be made, by way of example, to the accompanyingdrawings in which:

FIG. 1 is a block diagram of a mobile device in one exampleimplementation;

FIG. 2 is a block diagram of a communication subsystem component of themobile device of FIG. 1;

FIG. 3 is a block diagram of a node of a wireless network;

FIG. 4 is a block diagram illustrating components of a host system inone example configuration; and

FIG. 5 is a flowchart illustrating steps in a method of determining asecurity encoding to be applied to outgoing messages in one embodiment.

DETAILED DESCRIPTION

Embodiments described herein relate generally to systems and methods inwhich a security encoding to be applied to messages can be determinedwith minimal user intervention. In at least one embodiment, a policyengine to which the user's computing device is coupled dictates thesecurity encoding to be applied to messages being sent, anddeterminations of which security encoding is to be applied to any givenmessage are deferred to this policy engine. This may minimize or eveneliminate the need for a user to make security-related decisions whencomposing and sending messages. This can enhance usability of thecomputing device by making the process of sending messages moreefficient, which can be particularly advantageous when the computingdevice is a mobile device.

In one broad aspect, there is provided a method of determining asecurity encoding to be applied to a message being sent by a user of acomputing device, the method comprising the steps of: identifying amessage to be sent to at least one recipient; determining, at thecomputing device, whether a general message encoding configurationsetting thereon is set to a value that indicates that the securityencoding to be applied to the identified message is to be established bya policy engine; where the general message encoding configurationsetting on the computing device is set to a value that indicates thatthe security encoding to be applied to the identified message is to beestablished by the policy engine, determining the security encoding tobe applied to the identified message by querying the policy engine forthe security encoding to be applied to the identified message; applyingthe determined security encoding to the identified message; andtransmitting the identified message to which the security encoding hasbeen applied to the at least one recipient.

In another broad aspect, there is provided a system for determining asecurity encoding to be applied to a message being sent by a user of acomputing device, wherein the system comprises a policy engine connectedto the computing device, and wherein the steps of an embodiment of amethod as described herein are performed by the system.

In one embodiment, the policy engine is implemented in a device remotefrom the computing device. The computing device may be a mobile device,for example. The policy engine may be implemented in a PGP UniversalServer in PGP-based applications, for example.

These and other features of various embodiments will be described ingreater detail below.

Some embodiments of the systems and methods described herein makereference to a mobile device. A mobile device is a two-way communicationdevice with advanced data communication capabilities having thecapability to communicate with other computer systems. A mobile devicemay also include the capability for voice communications. Depending onthe functionality provided by a mobile device, it may be referred to asa data messaging device, a two-way pager, a cellular telephone with datamessaging capabilities, a wireless Internet appliance, or a datacommunication device (with or without telephony capabilities). A mobiledevice communicates with other devices through a network of transceiverstations.

To aid the reader in understanding the structure of a mobile device andhow it communicates with other devices, reference is made to FIGS. 1through 3.

Referring first to FIG. 1, a block diagram of a mobile device in oneexample implementation is shown generally as 100. Mobile device 100comprises a number of components, the controlling component beingmicroprocessor 102. Microprocessor 102 controls the overall operation ofmobile device 100. Communication functions, including data and voicecommunications, are performed through communication subsystem 104.Communication subsystem 104 receives messages from and sends messages toa wireless network 200. In this example implementation of mobile device100, communication subsystem 104 is configured in accordance with theGlobal System for Mobile Communication (GSM) and General Packet RadioServices (GPRS) standards. The GSM/GPRS wireless network is usedworldwide and it is expected that these standards will be supersededeventually by Enhanced Data GSM Environment (EDGE) and Universal MobileTelecommunications Service (UMTS). New standards are still beingdefined, but it is believed that they will have similarities to thenetwork behavior described herein, and it will also be understood bypersons skilled in the art that the invention is intended to use anyother suitable standards that are developed in the future. The wirelesslink connecting communication subsystem 104 with network 200 representsone or more different Radio Frequency (RF) channels, operating accordingto defined protocols specified for GSM/GPRS communications. With newernetwork protocols, these channels are capable of supporting both circuitswitched voice communications and packet switched data communications.

Although the wireless network associated with mobile device 100 is aGSM/GPRS wireless network in one example implementation of mobile device100, other wireless networks may also be associated with mobile device100 in variant implementations. Different types of wireless networksthat may be employed include, for example, data-centric wirelessnetworks, voice-centric wireless networks, and dual-mode networks thatcan support both voice and data communications over the same physicalbase stations. Combined dual-mode networks include, but are not limitedto, Code Division Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRSnetworks (as mentioned above), and future third-generation (3G) networkslike EDGE and UMTS. Some older examples of data-centric networks includethe Mobitex™ Radio Network and the DataTAC™ Radio Network. Examples ofolder voice-centric data networks include Personal Communication Systems(PCS) networks like GSM and Time Division Multiple Access (TDMA)systems.

Microprocessor 102 also interacts with additional subsystems such as aRandom Access Memory (RAM) 106, flash memory 108, display 110, auxiliaryinput/output (I/O) subsystem 112, serial port 114, keyboard 116, speaker118, microphone 120, short-range communications subsystem 122 and otherdevices 124.

Some of the subsystems of mobile device 100 performcommunication-related functions, whereas other subsystems may provide“resident” or on-device functions. By way of example, display 110 andkeyboard 116 may be used for both communication-related functions, suchas entering a text message for transmission over network 200, anddevice-resident functions such as a calculator or task list. Operatingsystem software used by microprocessor 102 is typically stored in apersistent store such as flash memory 108, which may alternatively be aread-only memory (ROM) or similar storage element (not shown). Thoseskilled in the art will appreciate that the operating system, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile store such as RAM 106.

Mobile device 100 may send and receive communication signals overnetwork 200 after required network registration or activation procedureshave been completed. Network access is associated with a subscriber oruser of a mobile device 100. To identify a subscriber, mobile device 100requires a Subscriber Identity Module or “SIM” card 126 to be insertedin a SIM interface 128 in order to communicate with a network. SIM 126is one type of a conventional “smart card” used to identify a subscriberof mobile device 100 and to personalize the mobile device 100, amongother things. Without SIM 126, mobile device 100 is not fullyoperational for communication with network 200. By inserting SIM 126into SIM interface 128, a subscriber can access all subscribed services.Services could include: web browsing and messaging such as e-mail, voicemail, Short Message Service (SMS), and Multimedia Messaging Services(MMS). More advanced services may include: point of sale, field serviceand sales force automation. SIM 126 includes a processor and memory forstoring information. Once SIM 126 is inserted in SIM interface 128, itis coupled to microprocessor 102. In order to identify the subscriber,SIM 126 contains some user parameters such as an International MobileSubscriber Identity (IMSI). An advantage of using SIM 126 is that asubscriber is not necessarily bound by any single physical mobiledevice. SIM 126 may store additional subscriber information for a mobiledevice as well, including datebook (or calendar) information and recentcall information.

Mobile device 100 is a battery-powered device and includes a batteryinterface 132 for receiving one or more rechargeable batteries 130.Battery interface 132 is coupled to a regulator (not shown), whichassists battery 130 in providing power V+ to mobile device 100. Althoughcurrent technology makes use of a battery, future technologies such asmicro fuel cells may provide the power to mobile device 100.

Microprocessor 102, in addition to its operating system functions,enables execution of software applications on mobile device 100. A setof applications that control basic device operations, including data andvoice communication applications, will normally be installed on mobiledevice 100 during its manufacture. Another application that may beloaded onto mobile device 100 would be a personal information manager(PIM). A PIM has functionality to organize and manage data items ofinterest to a subscriber, such as, but not limited to, e-mail, calendarevents, voice mails, appointments, and task items. A PIM application hasthe ability to send and receive data items via wireless network 200. PIMdata items may be seamlessly integrated, synchronized, and updated viawireless network 200 with the mobile device subscriber's correspondingdata items stored and/or associated with a host computer system. Thisfunctionality creates a mirrored host computer on mobile device 100 withrespect to such items. This can be particularly advantageous where thehost computer system is the mobile device subscriber's office computersystem.

Additional applications may also be loaded onto mobile device 100through network 200, auxiliary I/O subsystem 112, serial port 114,short-range communications subsystem 122, or any other suitablesubsystem 124. This flexibility in application installation increasesthe functionality of mobile device 100 and may provide enhancedon-device functions, communication-related functions, or both. Forexample, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing mobile device 100.

Serial port 114 enables a subscriber to set preferences through anexternal device or software application and extends the capabilities ofmobile device 100 by providing for information or software downloads tomobile device 100 other than through a wireless communication network.The alternate download path may, for example, be used to load anencryption key onto mobile device 100 through a direct and thus reliableand trusted connection to provide secure device communication.

Short-range communications subsystem 122 provides for communicationbetween mobile device 100 and different systems or devices, without theuse of network 200. For example, subsystem 122 may include an infrareddevice and associated circuits and components for short-rangecommunication. Examples of short range communication would includestandards developed by the Infrared Data Association (IrDA), Bluetooth,and the 802.11 family of standards developed by IEEE.

In use, a received signal such as a text message, an e-mail message, orweb page download will be processed by communication subsystem 104 andinput to microprocessor 102. Microprocessor 102 will then process thereceived signal for output to display 110 or alternatively to auxiliaryI/O subsystem 112. A subscriber may also compose data items, such ase-mail messages, for example, using keyboard 116 in conjunction withdisplay 110 and possibly auxiliary I/O subsystem 112. Auxiliarysubsystem 112 may include devices such as: a touch screen, mouse, trackball, infrared fingerprint detector, or a roller wheel with dynamicbutton pressing capability. Keyboard 116 is an alphanumeric keyboardand/or telephone-type keypad. A composed item may be transmitted overnetwork 200 through communication subsystem 104.

For voice communications, the overall operation of mobile device 100 issubstantially similar, except that the received signals would be outputto speaker 118, and signals for transmission would be generated bymicrophone 120. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on mobiledevice 100. Although voice or audio signal output is accomplishedprimarily through speaker 118, display 110 may also be used to provideadditional information such as the identity of a calling party, durationof a voice call, or other voice call related information.

Referring now to FIG. 2, a block diagram of the communication subsystemcomponent 104 of FIG. 1 is shown. Communication subsystem 104 comprisesa receiver 150, a transmitter 152, one or more embedded or internalantenna elements 154, 156, Local Oscillators (LOs) 158, and a processingmodule such as a Digital Signal Processor (DSP) 160.

The particular design of communication subsystem 104 is dependent uponthe network 200 in which mobile device 100 is intended to operate, thusit should be understood that the design illustrated in FIG. 2 servesonly as one example. Signals received by antenna 154 through network 200are input to receiver 150, which may perform such common receiverfunctions as signal amplification, frequency down conversion, filtering,channel selection, and analog-to-digital (A/D) conversion. A/Dconversion of a received signal allows more complex communicationfunctions such as demodulation and decoding to be performed in DSP 160.In a similar manner, signals to be transmitted are processed, includingmodulation and encoding, by DSP 160. These DSP-processed signals areinput to transmitter 152 for digital-to-analog (D/A) conversion,frequency up conversion, filtering, amplification and transmission overnetwork 200 via antenna 156. DSP 160 not only processes communicationsignals, but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in DSP 160.

The wireless link between mobile device 100 and a network 200 maycontain one or more different channels, typically different RF channels,and associated protocols used between mobile device 100 and network 200.A RF channel is a limited resource that must be conserved, typically dueto limits in overall bandwidth and limited battery power of mobiledevice 100.

When mobile device 100 is fully operational, transmitter 152 istypically keyed or turned on only when it is sending to network 200 andis otherwise turned off to conserve resources. Similarly, receiver 150is periodically turned off to conserve power until it is needed toreceive signals or information (if at all) during designated timeperiods.

Referring now to FIG. 3, a block diagram of a node of a wireless networkis shown as 202. In practice, network 200 comprises one or more nodes202. Mobile device 100 communicates with a node 202 within wirelessnetwork 200. In the example implementation of FIG. 3, node 202 isconfigured in accordance with General Packet Radio Service (GPRS) andGlobal Systems for Mobile (GSM) technologies. Node 202 includes a basestation controller (BSC) 204 with an associated tower station 206, aPacket Control Unit (PCU) 208 added for GPRS support in GSM, a MobileSwitching Center (MSC) 210, a Home Location Register (HLR) 212, aVisitor Location Registry (VLR) 214, a Serving GPRS Support Node (SGSN)216, a Gateway GPRS Support Node (GGSN) 218, and a Dynamic HostConfiguration Protocol (DHCP) 220. This list of components is not meantto be an exhaustive list of the components of every node 202 within aGSM/GPRS network, but rather a list of components that are commonly usedin communications through network 200.

In a GSM network, MSC 210 is coupled to BSC 204 and to a landlinenetwork, such as a Public Switched Telephone Network (PSTN) 222 tosatisfy circuit switched requirements. The connection through PCU 208,SGSN 216 and GGSN 218 to the public or private network (Internet) 224(also referred to herein generally as a shared network infrastructure)represents the data path for GPRS capable mobile devices. In a GSMnetwork extended with GPRS capabilities, BSC 204 also contains a PacketControl Unit (PCU) 208 that connects to SGSN 216 to controlsegmentation, radio channel allocation and to satisfy packet switchedrequirements. To track mobile device location and availability for bothcircuit switched and packet switched management, HLR 212 is sharedbetween MSC 210 and SGSN 216. Access to VLR 214 is controlled by MSC210.

Station 206 is a fixed transceiver station. Station 206 and BSC 204together form the fixed transceiver equipment. The fixed transceiverequipment provides wireless network coverage for a particular coveragearea commonly referred to as a “cell”. The fixed transceiver equipmenttransmits communication signals to and receives communication signalsfrom mobile devices within its cell via station 206. The fixedtransceiver equipment normally performs such functions as modulation andpossibly encoding and/or encryption of signals to be transmitted to themobile device in accordance with particular, usually predetermined,communication protocols and parameters, under control of its controller.The fixed transceiver equipment similarly demodulates and possiblydecodes and decrypts, if necessary, any communication signals receivedfrom mobile device 100 within its cell. Communication protocols andparameters may vary between different nodes. For example, one node mayemploy a different modulation scheme and operate at differentfrequencies than other nodes.

For all mobile devices 100 registered with a specific network, permanentconfiguration data such as a user profile is stored in HLR 212. HLR 212also contains location information for each registered mobile device andcan be queried to determine the current location of a mobile device. MSC210 is responsible for a group of location areas and stores the data ofthe mobile devices currently in its area of responsibility in VLR 214.Further VLR 214 also contains information on mobile devices that arevisiting other networks. The information in VLR 214 includes part of thepermanent mobile device data transmitted from HLR 212 to VLR 214 forfaster access. By moving additional information from a remote HLR 212node to VLR 214, the amount of traffic between these nodes can bereduced so that voice and data services can be provided with fasterresponse times and at the same time requiring less use of computingresources.

SGSN 216 and GGSN 218 are elements added for GPRS support; namely packetswitched data support, within GSM. SGSN 216 and MSC 210 have similarresponsibilities within wireless network 200 by keeping track of thelocation of each mobile device 100. SGSN 216 also performs securityfunctions and access control for data traffic on network 200. GGSN 218provides internetworking connections with external packet switchednetworks and connects to one or more SGSN's 216 via an Internet Protocol(IP) backbone network operated within the network 200. During normaloperations, a given mobile device 100 must perform a “GPRS Attach” toacquire an IP address and to access data services. This requirement isnot present in circuit switched voice channels as Integrated ServicesDigital Network (ISDN) addresses are used for routing incoming andoutgoing calls. Currently, all GPRS capable networks use private,dynamically assigned IP addresses, thus requiring a DHCP server 220connected to the GGSN 218. There are many mechanisms for dynamic IPassignment, including using a combination of a Remote AuthenticationDial-In User Service (RADIUS) server and DHCP server. Once the GPRSAttach is complete, a logical connection is established from a mobiledevice 100, through PCU 208, and SGSN 216 to an Access Point Node (APN)within GGSN 218. The APN represents a logical end of an IP tunnel thatcan either access direct Internet compatible services or private networkconnections. The APN also represents a security mechanism for network200, insofar as each mobile device 100 must be assigned to one or moreAPNs and mobile devices 100 cannot exchange data without firstperforming a GPRS Attach to an APN that it has been authorized to use.The APN may be considered to be similar to an Internet domain name suchas “myconnection.wireless.com”.

Once the GPRS Attach is complete, a tunnel is created and all traffic isexchanged within standard IP packets using any protocol that can besupported in IP packets. This includes tunneling methods such as IP overIP as in the case with some IPSecurity (Ipsec) connections used withVirtual Private Networks (VPN). These tunnels are also referred to asPacket Data Protocol (PDP) Contexts and there are a limited number ofthese available in the network 200. To maximize use of the PDP Contexts,network 200 will run an idle timer for each PDP Context to determine ifthere is a lack of activity. When a mobile device 100 is not using itsPDP Context, the PDP Context can be deallocated and the IP addressreturned to the IP address pool managed by DHCP server 220.

Referring now to FIG. 4, a block diagram illustrating components of ahost system in one example configuration is shown. Host system 250 willtypically be a corporate office or other local area network (LAN), butmay instead be a home office computer or some other private system, forexample, in variant implementations. In this example shown in FIG. 4,host system 250 is depicted as a LAN of an organization to which a userof mobile device 100 belongs.

LAN 250 comprises a number of network components connected to each otherby LAN connections 260. For instance, a user's desktop computing device(“desktop computer”) 262 a with an accompanying cradle 264 for theuser's mobile device 100 is situated on LAN 250. Cradle 264 for mobiledevice 100 may be coupled to computer 262 a by a serial or a UniversalSerial Bus (USB) connection, for example. Other user computers 262 b arealso situated on LAN 250, and each may or may not be equipped with anaccompanying cradle 264 for a mobile device. Cradle 264 facilitates theloading of information (e.g. PIM data, private symmetric encryption keysto facilitate secure communications between mobile device 100 and LAN250) from user computer 262 a to mobile device 100, and may beparticularly useful for bulk information updates often performed ininitializing mobile device 100 for use. The information downloaded tomobile device 100 may include S/MIME certificates or PGP keys used inthe exchange of messages. The process of downloading information from auser's desktop computer 262 a to the user's mobile device 100 may alsobe referred to as synchronization.

It will be understood by persons skilled in the art that user computers262 a, 262 b will typically be also connected to other peripheraldevices not explicitly shown in FIG. 4. Furthermore, only a subset ofnetwork components of LAN 250 are shown in FIG. 4 for ease ofexposition, and it will be understood by persons skilled in the art thatLAN 250 will comprise additional components not explicitly shown in FIG.4, for this example configuration. More generally, LAN 250 may representa smaller part of a larger network [not shown] of the organization, andmay comprise different components and/or be arranged in differenttopologies than that shown in the example of FIG. 4.

In this example, mobile device 100 communicates with LAN 250 through anode 202 of wireless network 200 and a shared network infrastructure 224such as a service provider network or the public Internet. Access to LAN250 may be provided through one or more routers [not shown], andcomputing devices of LAN 250 may operate from behind a firewall or proxyserver 266.

In a variant implementation, LAN 250 comprises a wireless VPN router[not shown] to facilitate data exchange between the LAN 250 and mobiledevice 100. The concept of a wireless VPN router is new in the wirelessindustry and implies that a VPN connection can be established directlythrough a specific wireless network to mobile device 100. Thepossibility of using a wireless VPN router has only recently beenavailable and could be used when the new Internet Protocol (IP) Version6 (IPV6) arrives into IP-based wireless networks. This new protocol willprovide enough IP addresses to dedicate an IP address to every mobiledevice, making it possible to push information to a mobile device at anytime. An advantage of using a wireless VPN router is that it could be anoff-the-shelf VPN component, not requiring a separate wireless gatewayand separate wireless infrastructure to be used. A VPN connection wouldpreferably be a Transmission Control Protocol (TCP)/IP or User DatagramProtocol (UDP)/IP connection to deliver the messages directly to mobiledevice 100 in this variant implementation.

Messages intended for a user of mobile device 100 are initially receivedby a message server 268 of LAN 250. Such messages may originate from anyof a number of sources. For instance, a message may have been sent by asender from a computer 262 b within LAN 250, from a different mobiledevice [not shown] connected to wireless network 200 or to a differentwireless network, or from a different computing device or other devicecapable of sending messages, via the shared network infrastructure 224,and possibly through an application service provider (ASP) or Internetservice provider (ISP), for example.

Message server 268 typically acts as the primary interface for theexchange of messages, particularly e-mail messages, within theorganization and over the shared network infrastructure 224. Each userin the organization that has been set up to send and receive messages istypically associated with a user account managed by message server 268.One example of a message server 268 is a Microsoft Exchange™ Server. Insome implementations, LAN 250 may comprise multiple message servers 268.Message server 268 may also be adapted to provide additional functionsbeyond message management, including the management of data associatedwith calendars and task lists, for example.

When messages are received by message server 268, they are typicallystored in a message store [not explicitly shown], from which messagescan be subsequently retrieved and delivered to users. For instance, ane-mail client application operating on a user's computer 262 a mayrequest the e-mail messages associated with that user's account storedon message server 268. These messages would then typically be retrievedfrom message server 268 and stored locally on computer 262 a.

When operating mobile device 100, the user may wish to have e-mailmessages retrieved for delivery to the handheld. An e-mail clientapplication operating on mobile device 100 may also request messagesassociated with the user's account from message server 268. The e-mailclient may be configured (either by the user or by an administrator,possibly in accordance with an organization's information technology(IT) policy) to make this request at the direction of the user, at somepre-defined time interval, or upon the occurrence of some pre-definedevent. In some implementations, mobile device 100 is assigned its owne-mail address, and messages addressed specifically to mobile device 100are automatically redirected to mobile device 100 as they are receivedby message server 268.

To facilitate the wireless communication of messages and message-relateddata between mobile device 100 and components of LAN 250, a number ofwireless communications support components 270 may be provided. In thisexample implementation, wireless communications support components 270comprise a message management server 272, for example. Messagemanagement server 272 is used to specifically provide support for themanagement of messages, such as e-mail messages, that are to be handledby mobile devices. Generally, while messages are still stored on messageserver 268, message management server 272 can be used to control when,if, and how messages should be sent to mobile device 100. Messagemanagement server 272 also facilitates the handling of messages composedon mobile device 100, which are sent to message server 268 forsubsequent delivery.

For example, message management server 272 may: monitor the user's“mailbox” (e.g. the message store associated with the user's account onmessage server 268) for new e-mail messages; apply user-definablefilters to new messages to determine if and how the messages will berelayed to the user's mobile device 100; compress and encrypt newmessages (e.g. using an encryption technique such as Data EncryptionStandard (DES) or Triple DES) and push them to mobile device 100 via theshared network infrastructure 224 and wireless network 200; and receivemessages composed on mobile device 100 (e.g. encrypted using TripleDES), decrypt and decompress the composed messages, re-format thecomposed messages if desired so that they will appear to have originatedfrom the user's computer 262 a, and re-route the composed messages tomessage server 268 for delivery.

Certain properties or restrictions associated with messages that are tobe sent from and/or received by mobile device 100 can be defined (e.g.by an administrator in accordance with IT policy) and enforced bymessage management server 272. These may include whether mobile device100 may receive encrypted and/or signed messages, minimum encryption keysizes, whether outgoing messages must be encrypted and/or signed, andwhether copies of all secure messages sent from mobile device 100 are tobe sent to a pre-defined copy address, for example.

Message management server 272 may also be adapted to provide othercontrol functions, such as only pushing certain message information orpre-defined portions (e.g. “blocks”) of a message stored on messageserver 268 to mobile device 100. For example, when a message isinitially retrieved by mobile device 100 from message server 268,message management server 272 is adapted to push only the first part ofa message to mobile device 100, with the part being of a pre-definedsize (e.g. 2 KB). The user can then request more of the message, to bedelivered in similar-sized blocks by message management server 272 tomobile device 100, possibly up to a maximum pre-defined message size.

Accordingly, message management server 272 facilitates better controlover the type of data and the amount of data that is communicated tomobile device 100, and can help to minimize potential waste of bandwidthor other resources.

It will be understood by persons skilled in the art that messagemanagement server 272 need not be implemented on a separate physicalserver in LAN 250 or other network. For example, some or all of thefunctions associated with message management server 272 may beintegrated with message server 268, or some other server in LAN 250.Furthermore, LAN 250 may comprise multiple message management servers272, particularly in variant implementations where a large number ofmobile devices need to be supported.

In some embodiments described herein, certificates are used in theprocessing of encoded messages, such as e-mail messages, that areencrypted and/or signed. While Simple Mail Transfer Protocol (SMTP),RFC822 headers, and Multipurpose Internet Mail Extensions (MIME) bodyparts may be used to define the format of a typical e-mail message notrequiring encoding, Secure/MIME (S/MIME), a version of the MIMEprotocol, may be used in the communication of encoded messages (i.e. insecure messaging applications). S/MIME enables end-to-end authenticationand confidentiality, and provides data integrity and privacy from thetime an originator of a message sends a message until it is decoded andread by the message recipient. In other embodiments of described herein,other standards and protocols may be employed to facilitate securemessage communication, such as Pretty Good Privacy™ (PGP) and variantsof PGP such as OpenPGP, for example. It will be understood that wherereference is generally made to “PGP” herein, the term is intended toencompass any of a number of variant implementations based on the moregeneral PGP scheme.

Secure messaging protocols such as S/MIME and PGP-based protocols relyon public and private encryption keys to provide confidentiality andintegrity. Data encoded using a private key of a private key/public keypair can only be decoded using the corresponding public key of the pair,and vice-versa. It is intended that private key information never bemade public, whereas public key information is shared.

For example, if a sender wishes to send a message to a recipient inencrypted form, the recipient's public key is used to encrypt a message,which can then be decrypted only using the recipient's private key.Alternatively, in some encoding techniques, a one-time session key isgenerated and used to encrypt the body of a message, typically with asymmetric encryption technique (e.g. Triple DES). The session key isthen encrypted using the recipient's public key (e.g. with a public keyencryption algorithm such as RSA), which can then be decrypted onlyusing the recipient's private key. The decrypted session key can then beused to decrypt the message body. The message header may be used tospecify the particular encryption scheme that must be used to decryptthe message. Other encryption techniques based on public keycryptography may be used in variant implementations. However, in each ofthese cases, only the recipient's private key may be used to facilitatesuccessful decryption of the message, and in this way, theconfidentiality of messages can be maintained.

As a further example, a sender may sign a message using a digitalsignature. A digital signature is a digest of the message (e.g. a hashof the message) encoded using the sender's private key, which can thenbe appended to the outgoing message. To verify the digital signature ofthe message when received, the recipient uses the same technique as thesender (e.g. using the same standard hash algorithm) to obtain a digestof the received message. The recipient also uses the sender's public keyto decode the digital signature, in order to obtain what should be amatching digest for the received message. If the digests of the receivedmessage do not match, this suggests that either the message content waschanged during transport and/or the message did not originate from thesender whose public key was used for verification. Digital signaturealgorithms are designed in such a way that only someone with knowledgeof the sender's private key should be able to encode a signature thatthe recipient will decode correctly using the sender's public key.Therefore, by verifying a digital signature in this way, authenticationof the sender and message integrity can be maintained.

An encoded message may be encrypted, signed, or both encrypted andsigned. In S/MIME, the authenticity of public keys used in theseoperations is validated using certificates. A certificate is a digitaldocument issued by a certificate authority (CA). Certificates are usedto authenticate the association between users and their public keys, andessentially, provides a level of trust in the authenticity of the users'public keys. Certificates contain information about the certificateholder, with certificate contents typically formatted in accordance withan accepted standard (e.g. X.509). The certificates are typicallydigitally signed by the certificate authority.

In PGP-based systems, a PGP key is used, which is like a certificate inthat it contains public information including a public key andinformation on the key holder or owner. Unlike S/MIME certificates,however, PGP keys are not generally issued by a certificate authority,and the level of trust in the authenticity of a PGP key typicallyrequires verifying that a trusted individual has vouched for theauthenticity of a given PGP key.

Standard e-mail security protocols typically facilitate secure messagetransmission between non-mobile computing devices (e.g. computers 262 a,262 b of FIG. 4; remote desktop devices). In order that signed messagesreceived from senders may be read from mobile device 100 and thatencrypted messages be sent from mobile device 100, mobile device 100 isadapted to store public keys (e.g. in S/MIME certificates, PGP keys) ofother individuals. Keys stored on a user's computer 262 a will typicallybe downloaded from computer 262 a to mobile device 100 through cradle264, for example.

Mobile device 100 may also be adapted to store the private key of thepublic key/private key pair associated with the user, so that the userof mobile device 100 can sign outgoing messages composed on mobiledevice 100, and decrypt messages sent to the user encrypted with theuser's public key. The private key may be downloaded to mobile device100 from the user's computer 262 a through cradle 264, for example. Theprivate key is preferably exchanged between the computer 262 a andmobile device 100 so that the user may share one identity and one methodfor accessing messages.

User computers 262 a, 262 b can obtain S/MIME certificates and PGP keysfrom a number of sources, for storage on computers 262 a, 262 b and/ormobile devices (e.g. mobile device 100). These certificate sources maybe private (e.g. dedicated for use within an organization) or public,may reside locally or remotely, and may be accessible from within anorganization's private network or through the Internet, for example. Inthe example shown in FIG. 4, multiple PKI servers 280 associated withthe organization reside on LAN 250. PKI servers 280 include a CA server282 for issuing S/MIME certificates, an LDAP server 284 used to searchfor and download S/MIME certificates and/or PGP keys (e.g. forindividuals within the organization), and an OCSP server 286 used toverify the revocation status of S/MIME certificates.

Certificates and/or PGP keys may be retrieved from LDAP server 284 by auser computer 262 a, for example, to be downloaded to mobile device 100via cradle 264. However, in a variant implementation, LDAP server 284may be accessed directly (i.e. “over the air” in this context) by mobiledevice 100, and mobile device 100 may search for and retrieve individualcertificates and PGP keys through a mobile data server 288. Similarly,mobile data server 288 may be adapted to allow mobile device 100 todirectly query OCSP server 286 to verify the revocation status of S/MIMEcertificates.

In variant implementations, only selected PKI servers 280 may be madeaccessible to mobile devices (e.g. allowing certificates to bedownloaded only from a user's computer 262 a, 262 b, while allowing therevocation status of certificates to be checked from mobile device 100).

In variant implementations, certain PKI servers 280 may be madeaccessible only to mobile devices registered to particular users, asspecified by an IT administrator, possibly in accordance with an ITpolicy, for example.

Other sources of certificates and PGP keys [not shown] may include aWindows certificate or key store, another secure certificate or keystore on or outside LAN 250, and smart cards, for example.

In at least one embodiment, a policy engine 290 resides in LAN 250. Insome embodiments of the systems and methods described herein, the policyengine 290 is provided by way of a PGP Universal Server developed by PGPCorporation. This is only one example. In variant embodiments, thepolicy engine may be implemented in some other device or construct otherthan a PGP Universal Server, and may be applied in the context ofprotocols other than PGP (e.g. in an S/MIME policy engine).

A PGP Universal Server 290 is adapted to communicate with a user'sdesktop computer (e.g. 262 a) and the user's mobile device (e.g. 100 viamessage management server 272), and may be further adapted to encryptmessages and enforce compliance of security requirements with respect tomessages being sent by the user, based on policies established by anadministrator, for example. The placement of PGP Universal Server 290 inLAN 250 as shown in FIG. 4 is provided by way of example only, and otherplacements and configurations are possible. Depending on the placementof the PGP Universal Server 290 and the particular configuration of LAN250 in which PGP Universal Server 290 may be employed, the level ofcontrol over processed messages that are subject to security encoding,and in particular, over messages being sent by a user, may vary.

For example, PGP Universal Server 290 may be adapted to directly processall outgoing messages (i.e. messages being sent by the user from theuser's desktop computer, mobile device, or other computing device to oneor more intended recipients), where it will make decisions on whichmessages to encrypt and/or sign, if at all, in accordance with policiesdefined on the PGP Universal Server 290 as configured by theadministrator. If a policy dictates that a message about to be sent bythe user to a particular domain or pertaining to a particular subject isto be encrypted and signed using PGP for example, the PGP UniversalServer 290 may itself encrypt and sign the message before transmission.Alternatively, the user (e.g. through a PGP-enabled client applicationon the user's computing device that communicates with PGP UniversalServer 290) may download policy data from the PGP Universal Server 290to the user's computing device, and be directed to encrypt and sign themessage before transmission, based on the policy data obtained.

Accordingly, PGP Universal Server 290 provides the ability to enforcecentralized policy based on domains and other mechanisms.

The PGP Universal Server 290 may also be adapted to store, validate, andotherwise manage PGP keys, and to retrieve PGP keys from remote keystores when the keys are required to encode (e.g. encrypt and/or sign)messages. Where requested by a user (e.g. through a PGP clientapplication), PGP Universal Server 290 may also provide stored orretrieved PGP keys to the user as needed.

By adopting the use of a policy engine such as that implemented by a PGPUniversal Server 290 as described herein by way of example, much of theburden associated with processing secure messages (e.g. e-mail), and inparticular, with deciding what messages are to be sent securely and whatsecurity encoding should apply on a case-by-case basis, can betransferred to the policy engine.

In a typical known system, when a user sends a message from a computingdevice such as a desktop computer or mobile device, for example, themessage may be signed and/or encrypted at the user's option. Some userswill prefer to select a specific security encoding for messages thatthey compose (e.g. they will want to decide whether to send the messageas plain text, sign the message, encrypt the message, or both sign andencrypt the message) on a message-by-message basis.

Furthermore, an application (e.g. an e-mail client or other messagingapplication) residing and executing on the computing device may beconfigured to suggest a security encoding for outgoing messages based onone or more security encoding selection algorithms. For example, if theapplication determines that a message to be sent is a “reply” message ora “forward” message derived from a message previously received by theuser, the application may suggest to the user that the security encodingused in the original message should also be applied to the message to besent. As a further example, if the messaging application manages arecipient cache, which stores data that tracks particular securityencodings that have been associated with specific recipients (e.g. itcan track which security encoding was used when the user last sent amessage to a particular recipient), the application may suggest to theuser that the same security encoding be used when a subsequent messageis sent to the same recipient, as identified from data is stored in therecipient cache. The application may also be configured to apply somedefault security encoding (e.g. PGP—[Encrypt Only]) whenever a securityencoding cannot be determined based on these or other selectionalgorithms that may be applied.

In contrast to known systems, in systems that provide for a policyengine such as a PGP Universal Server 290, the need for users tomanually decide what security encoding should be applied to a givenmessage may be eliminated.

Embodiments of systems and methods described herein permit users todefer to the encoding policies as defined at a policy engine, such asthe PGP Universal Server in one example, in the making ofencoding-related decisions.

A general message encoding configuration setting, which may also bereferred to as a “Global Default” setting, is configurable through anapplication on the computing device. This setting can be set to a valuethat indicates that the security encoding to be applied to a messagesent from the computing device is to be established by the policyengine. Where the general message encoding configuration setting is setto this value, the application will rely on the policy engine to dictatethe security encoding requirements for any message sent from thecomputing device.

In one embodiment, where the general message encoding configurationsetting is set to a value that indicates that the security encoding tobe applied to a message sent from the computing device is to beestablished by the policy engine, the security encoding would no longerbe determined in accordance with a security encoding selection algorithm(e.g. encodings based on a previously received message or on data in arecipient cache) as the security encodings defined by the policy enginewill take precedence.

In another embodiment, where the general message encoding configurationsetting is set to a value that indicates that the security encoding tobe applied to a message sent from the computing device is to beestablished by the policy engine, a user is not permitted to overridethe security encoding that is to be applied to a message with some otheruser-selected security encoding, as the security encodings defined bythe policy engine will take precedence. Furthermore, where the generalmessage encoding configuration setting is set to a value that indicatesthat the security encoding to be applied to a message sent from thecomputing device is to be established by the policy engine, the user maynot be prompted about any difficulties in processing the message (e.g.when encryption keys cannot be found for a recipient), as resolution ofthese problems would also be deferred to the policy engine.

Conceptually, at least some of the features of these embodiments allow a“Novice User” security mode to be provided, where the user can choose tosimply accept the security encoding policies as dictated by the policyengine (e.g. the PGP Universal Server), and need not be prompted toconfirm security encodings that are to be used when sending messages.This may make the process of sending encoded messages simpler from theuser's perspective and more efficient.

If the user wishes to retain manual control over which securityencodings are to be applied to messages that he or she sends, and/or tore-activate the application of one or more security encoding selectionalgorithms, the user may change the value of the general messageencoding configuration setting to one that does not indicate that thesecurity encoding to be applied to the identified message is to beestablished by the policy engine. In one embodiment, the value of thegeneral message encoding configuration setting may instead be set todefine some specific default security encoding (e.g. PGP [Encryptonly]), for example. The value of the general message encodingconfiguration setting may also be set through IT Policy in a variantembodiment.

Referring to FIG. 5, a flowchart illustrating steps in a method ofdetermining a security encoding to be applied to outgoing messages inone embodiment is shown generally as 300. Further details with respectto various steps of method 300 and with respect to features that may beemployed in variant embodiments have been discussed earlier in thisspecification.

Reference is made in method 300 to outgoing messages, which are ingeneral, messages composed by a user that are in the process of beingsent from a computing device to one or more recipients. The computingdevice may be a desktop computer (which may, for instance, include alaptop computer or some other computing device that a mobile device maysynchronize with), a mobile device, or some other device that cancommunicate with a policy engine (e.g. PGP Universal Server 290 of FIG.4). The policy engine will typically be implemented in a device remotelylocated from the computing device (i.e. not directly implemented on thecomputing device itself), but may nevertheless reside in the samenetwork (e.g. LAN 250).

At least some of the steps of method 300 are performed by an applicationexecuting and residing on the computing device. The application may bean e-mail or other messaging application, another application coupled toor otherwise integrated with the e-mail or other messaging application(e.g. an add-on component providing the requisite functionality), orsome other application programmed to perform such steps. Depending onthe configuration of the particular system embodiment, some steps ofmethod 300 may be performed by the policy engine coupled to thecomputing device.

At step 310, a message to be sent to at least one recipient isidentified at the computing device.

At step 320, it is determined whether a general message encodingconfiguration setting at the computing device is set to a value thatindicates that the security encoding to be applied to the identifiedmessage is to be established by a policy engine.

In one embodiment, the general message encoding configuration setting isidentified as a “Global Default” setting on the computing device, whichcan be configured by a user, or possibly through an IT Policy. Forexample, in a list of configuration settings, the user may set the“Global Default” setting associated with the encoding of outgoingmessages as follows:

-   -   Global Default: [PGP Universal Default] (Novice Mode)        In this particular implementation, by setting “Global Default”        to “[PGP Universal Default] (Novice Mode)”, this indicates that        the application must defer to the security encoding policies of        the policy engine (e.g. the PGP Universal Server) to determine        the appropriate encoding for an outgoing message. In one        embodiment, when the “Global Default” is set in this way,        security encoding selection algorithms that would normally be        relied upon to suggest a security encoding would not be applied,        and the user would not be prompted or permitted to manually        select a security encoding. On the other hand, if the “Global        Default” has been set to some other value that does not        specifically indicate that the security encoding is to be        established by the policy engine, such as:    -   e.g. Global Default: [PGP—Encrypt] or    -   Global Default: [PGP—Sign and Encrypt] or    -   Global Default: [PGP—Encrypt Only] or    -   Global Default: [plain text],        the security encoding selection algorithms may be relied upon to        suggest a security encoding for a particular message (e.g.        encodings based on a previously received message or on data in a        recipient cache), and the current value of the “Global Default”        setting may be used to suggest a default security encoding when        one cannot be determined from these selection algorithms, in        this embodiment. It will be understood that different selection        algorithms other than those described herein may be employed in        variant implementations.

In a variant embodiment, the general message encoding configurationsetting may alternatively be provided as an “on/off” or other Boolean ormulti-state flag, such that when the value of the setting is “on”, thiswould indicate that the security encoding to be applied to theidentified message is to be established by the policy engine. In oneexample, the value of a general message encoding configuration settingmay be set as follows:

-   -   PGP Universal Server Encoding Override: [on]

Where the general message encoding configuration setting on thecomputing device is set to a value that indicates that the securityencoding to be applied to the identified message is to be established bythe policy engine, at step 330, the security encoding to be applied tothe identified message is determined by querying the policy engine forthat security encoding.

In one system embodiment, the encoding (e.g. encryption and/or signing)of messages, where required, is performed at the computing device. Inthis case, the application residing on the computing device may querythe policy engine and download policy data from the policy engine todetermine the appropriate security encoding for the identified message.For example, the downloaded policy data may indicate that messages to besent to particular identified domains are to be encoded in a mannerspecific to those respective domains. Alternatively, the downloadedpolicy data may indicate that messages pertaining to particularidentified subjects are to be encoded in a manner specific to thoserespective subjects. Other mechanisms to implement different securityencoding policies may be employed.

In another system embodiment, messages are transmitted via the policyengine, which directly performs the necessary encoding (e.g. encryptionand/or signing) of messages where required. In this case, policy datatypically stored local to and accessible by the policy engine is queriedto determine the appropriate security encoding for the identifiedmessage.

At step 340, the determined security encoding is applied to the messageidentified at step 310. This step may be performed at the computingdevice or by the policy engine, depending on the configuration of theparticular system embodiment.

As noted in this specification, in exemplary embodiments, the step ofapplying a security encoding to a message entails one of the following:encrypting the message, signing the message, encrypting and signing themessage, and neither encrypting nor signing the message.

At step 350, the message to which the security encoding is applied atstep 340 is transmitted to the at least one recipient in known manner.

It will be understood that the features described herein may also beapplied in systems facilitating secure message transmission employingdifferent encoding techniques other than PGP, and/or where a policyengine or server other than a PGP Universal Server is employed, whichdictates and/or enforces specific encodings (i.e. whether a message isto be encrypted and/or signed) for messages being sent by a user.

The steps of the methods described herein may be provided as executablesoftware instructions stored on computer-readable media, which mayinclude transmission-type media.

The invention has been described with regard to a number of embodiments.However, it will be understood by persons skilled in the art that othervariants and modifications may be made without departing from the scopeof the invention as defined in the claims appended hereto.

1. A method of determining a security encoding to be applied to amessage being sent from a computing device to at least one recipient,the method comprising the steps of: determining, at the computingdevice, whether a general message encoding configuration selling thereonis set to a value that indicates that the security encoding to beapplied to the message is to be established by a policy engine; if thegeneral message encoding configuration selling on the computing deviceis set to a value that indicates that the security encoding to beapplied to the message is to be established by the policy engine,determining the security encoding to be applied to the message byquerying the policy engine for the security encoding to be applied tothe message; determining the security encoding to be applied to themessage in accordance with a security encoding selection process if thegeneral message encoding configuration selling on the computing deviceis not set to a value that indicates that the security encoding to beapplied to the message is to be established by the policy engine;applying the determined security encoding to the message; andtransmitting the message, to which the security encoding has beenapplied, to the at least one recipient; wherein the message is derivedfrom a second message previously received at the computing device; andwherein the security encoding selection process requires that the samesecurity encoding be applied to the message as the security encodingapplied to the second message previously received at the computingdevice.
 2. The method of claim 1, wherein the policy engine resides on adevice remote from the computing device.
 3. The method of claim 1,wherein the policy engine is implemented in a PGP Universal Server. 4.The method of claim 1, wherein the applying the determined securityencoding for the message comprises one of: encrypting the message;signing the message; encrypting and signing the message; or neitherencrypting nor signing the message.
 5. The method of claim 1, whereinthe computing device comprises one of: a desktop computer; or a mobiledevice.
 6. A physical computer-readable storage medium upon which aplurality of instructions are stored, the instructions for performing amethod of determining a security encoding to be applied to a messagebeing from a computing device to at least one recipient, the methodcomprising: determining, at the computing device, whether a generalmessage encoding configuration setting thereon is set to a value thatindicates that the security encoding to be applied to the message is tobe established by a policy engine; if the general message encodingconfiguration setting on the computing device is set to a value thatindicates that the security encoding to be applied to the message is tobe established by the policy engine, determining the security encodingto be applied to the message by querying the policy engine for thesecurity encoding to be applied to the message; determining the securityencoding to be applied to the message in accordance with a securityencoding selection process if the general message encoding configurationsetting on the computing device is not set to a value that indicatesthat the security encoding to be applied to the message is to beestablished by the policy engine; applying the determined securityencoding to the message; and transmitting the message, to which thesecurity encoding has been applied, to the at least one recipient;wherein the message is derived from a second message previously receivedat the computing device, and wherein the security encoding selectionprocess requires that the same security encoding be applied to themessage as the security encoding applied to the second messagepreviously received at the computing device.
 7. The medium of claim 6,wherein the policy engine resides on a device remote from the computingdevice.
 8. The medium of claim 6, wherein the policy engine isimplemented in a PGP Universal Server.
 9. The medium of claim 6, whereinthe applying the determined security encoding for the message comprisesone of: encrypting the message; signing the message; encrypting andsigning the message; or neither encrypting nor signing the message. 10.The medium of claim 6, wherein the computing device comprises one of: adesktop computer; or a mobile device.
 11. A system for determining asecurity encoding to be applied to a message being sent from a computingdevice to at least one recipient, wherein the system comprises a policyengine connected to the computing device, and wherein the system isconfigured to: determine, at the computing device, whether a generalmessage encoding configuration setting thereon is set to a value thatindicates that the security encoding to be applied to the message is tobe established by a policy engine; if the general message encodingconfiguration setting on the computing device is set to a value thatindicates that the security encoding to be applied to the message is tobe established by the policy engine, determine the security encoding tobe applied to the message by querying the policy engine for the securityencoding to be applied to the message; determine the security encodingto be applied to the message in accordance with a security encodingselection process if the general message encoding configuration settingon the computing device is not set to a value that indicates that thesecurity encoding to be applied to the message is to be established bythe policy engine; apply the determined security encoding to themessage; and transmit the message, to which the security encoding hasbeen applied, to the at least one recipient; wherein the message isderived from a second message previously received at the computingdevice, and wherein the security encoding selection process requiresthat the same security encoding be applied to the message as thesecurity encoding applied to the second message previously received atthe computing device.
 12. The system of claim 11, wherein the policyengine resides on a device remote from the computing device.
 13. Thesystem of claim 11, wherein the policy engine is implemented in a PGPUniversal Server.
 14. The system of claim 11, wherein the policy engineis configured to apply the determined security encoding to the message:and to transmit the message, to which the security encoding has beenapplied, to the at least one recipient.
 15. The system of claim 11,wherein in an application of the determined security encoding to themessage, the system is configured to perform one of: encrypting themessage; signing the message; encrypting and signing the message; orneither encrypting nor signing the message.
 16. The system of claim 11,wherein the computing device comprises one of: a desktop computer; or amobile device.